Restructure pkg/unittest and pkg/webdriver to follow the pub conventions.

tests/html/measurement_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#library('MeasurementTest');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
-#import('dart:html');
+library MeasurementTest;
+import '../../pkg/unittest/lib/unittest.dart';
+import '../../pkg/unittest/lib/html_config.dart';
+import 'dart:html';
 
 main() {
   useHtmlConfiguration();
 
   test('measurement is async but before setTimout 0', () {
     final element = document.body;
     bool fnComplete = false;
     bool timeout0 = false;
     window.setTimeout(() { timeout0 = true; }, 0);
     final computedStyle = element.computedStyle;
@@ skipping 17 matching lines @@
     final element = document.body;
     rect = element.rect;
     computedStyle = element.computedStyle;
     expect(rect.isComplete, isFalse);
     expect(computedStyle.isComplete, isFalse);
   });
 
   // TODO(jacobr): add more tests that the results return by measurement
   // functions are correct.
 }